illustration (attribution, if any possible, is at the end of the article)

If you love, love openly

Twenty monks and one nun, who was named Eshun, were practising meditation with a certain Zen master.
Eshun was very pretty even though her head was shaved and her dress plain. Several monks secretly fell in love with her. One of them wrote her a love letter, insisting upon a private meeting.
Eshun did not reply. The following day the master gave a lecture to the group, and when it was over, Eshun arose. Addressing the one who had written her, she said: «If you really love me so much, come and embrace me now.»

— from "Zen Flesh, Zen Bones: A Collection of Zen and Pre-zen Writings", edited by Paul Reps and Nyogen Senzaki

What was the failing of the monk?

Falling in 'love'? Cultivating deceit and pretence? Calling 'love' what was merely lust? Focusing on his feelings only? Clinging to and trying to protect an identity he was not (neither 'ultimately' nor even 'conventionally')? Clinging to and trying to protect the safety of his social position? Anything? What was the failing of the monk?